This invention relates to improving connections between nodes on different networks.
The use of small networks such as those found in small office/home office (SOHO) and residential settings is growing rapidly. Such private networks are typically connected to a larger public network (such as the Internet) through a gateway with a single internet protocol (IP) address that is valid on the public network. Nodes on the private network typically do not have IP addresses that are valid on the public network.
In order for nodes on the public network to transmit packets to nodes on the private network, the packets must be addressed to the public IP address of the gateway, which must then determine which node on the private network is the intended recipient. One common approach to this problem is Network Address Port Translation (NAPT). In a NAPT gateway, particular public network sockets of the gateway are mapped to particular sockets on nodes of the private network. Thus, when a packet from the public network is received on a particular socket at the network gateway, it is automatically forwarded to the socket on the private network to which the public network socket is mapped.
A scheme for NAPT is described in P. Srisuresh and K. Egevang, “Traditional IP Network Address Translator” published by the Internet Engineering Task Force in September, 1999, and available at http://www.ietf.cnri.reston.va.us/internet-drafts/draft-ietf-nat-traditional-03.txt. The NAPT scheme enables public network sockets to be dynamically mapped to private network sockets when a network connection is initiated from a private network socket. However, under the NAPT scheme connection requests originating from public network nodes can be processed by the gateway only if one of the gateway's public network sockets has been previously mapped to a socket on one of the private network nodes. This mapping must be done manually by a user at the gateway.
Other methods for establishing connectivity between public network sockets and private network sockets are described in M. Leech, et al., “RFC1928: SOCKS Protocol Version 5” published by the Internet Engineering Task Force in March, 1996 and available at http://www.ietf.cnri.reston.va.us/rfc/rfc1928.txt (describing the SOCKS protocol), and in M. Borella & D. Grabelsky, “Realm Specific IP: Protocol Specification” published by the Internet Engineering Task Force in August, 1999 and available at http://www.ietf.cnri.reston.va.us/internet-drafts/draft-ietf-nat-rsip-protocol-02.txt (describing the RSIP protocol). In both of these methods, connection requests received from the public network by the gateway are processed based on a previous mapping of the socket on which the request was received to a particular private network socket. In both SOCKS and RSIP, socket mapping is done in response to specific requests received by the gateway from particular private network nodes, on a first-come-first-serve basis.
For the purposes of this application, a “port” refers to a logical network connection point having a unique identifier with respect to a particular network node. For example, in the internet protocol, each network node may engage in multiple simultaneous connections on distinct numbered ports, e.g. port 25. A “socket” refers to a particular port on a particular node, and is referred to by the concatenation of a network address and a port identifier.